Heretofore, automotive drivelines employ a constant velocity joint for connecting a transmission shaft to another transmission shaft and transmitting rotational power to the axles.
One conventional constant velocity joint, whose technical concept is disclosed in Japanese Laid-Open Patent Publication No. 10-184717, has, as shown in FIG. 27 of the accompanying drawings, a roller 1 having a cylindrical inner circumferential wall surface 2 and a pair of flanges mounted on the respective axial ends of the cylindrical inner circumferential wall surface 2 for preventing rolling elements 3 (rolls, needles, or the like) from being dislodged. The constant velocity joint is assembled as follows: A plurality of rolling elements 3, whose number is one less than all of the rolling elements 3 to be finally mounted, is arrayed between the flanges on the cylindrical inner circumferential wall surface 2. The dimensions of the cylindrical inner circumferential wall surface 2 and the rolling elements 3 are selected such that the minimum distance d2 between two rolling elements 3 on the ends of the array is smaller than the diameter d1 of a rolling element 3a which is to be added finally between those two rolling elements 3 (d2<d1). The difference between the distance d2 and the diameter d1 serves as an interference ranging from several μm to several tens of μm. Then, the final rolling element 3a is pressed in between the two rolling elements 3 radially toward the cylindrical inner circumferential wall surface 2, thus installing the rolling elements 3 on the cylindrical inner circumferential wall surface 2.
The above process of arraying the rolling elements 3 along the cylindrical inner circumferential wall surface 2 of the roller 1 is referred to as a keystone process. The keystone process allows the roller 1 and the rolling elements 3 to be integrally combined as an inseparable assembly, which is assembled on an unillustrated leg shaft.
According to the assembling process disclosed in Japanese Laid-Open Patent Publication No. 10-184717, the interference needs to be provided for the final rolling element 3a to be pressed into the gap between the two rolling elements 3 for the purpose of achieving the keystone effect. To provide the interference, the inside diameter tolerance of the cylindrical inner circumferential wall surface 2 of the roller 1 and the outside diameter tolerances of the rolling elements 3, 3a have to be as small as possible.
If the above tolerances, i.e., the inside diameter tolerance and the outside diameter tolerances, are relatively large, then the interference may be eliminated, making the final rolling element 3a loose between the two rolling elements 3, or the interference may become so large that the final rolling element 3a cannot be pressed in between the two rolling elements 3 or, even if the final rolling element 3a can be pressed in between the two rolling elements 3, the rolling elements 3, 3a may be unduly deformed. Efforts to make the tolerances smaller result in difficulties machining the cylindrical inner circumferential wall surface 2 of the roller 1 and the rolling elements 3, 3a and an increase in the manufacturing cost. Furthermore, because of the need to press the final rolling elements 3a into the gap between the two rolling elements 3, the processing of assembling the roller 1 and the rolling elements 3, 3a into a roller unit is not easy to perform and is highly costly.